How to find out the differences between 2 objects in Java (2023)

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In this post, we will showcase a step-by-step guide on how to detect and present distinctions between two java objects by leveraging a set of classes and interfaces provided by Apache Commons Lang.

Classes, Interfaces, and pom.xml

The classes and interfaces to be used for this post are as follows:

<dependencies>
  <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-lang3</artifactId>
      <version>3.6</version>
  </dependency>
</dependencies>

Scenario

We have two Employee Object for our use case, and we need to list the differences between them. The list must show the affected field and the old-new (from Employee 1 to Employee 2 values.

Employee Object 1

For the Employee Object, we have the following data.

Name = Ankit
ID = 1
Designation = Assistant Vice President
Address = Mumbai

Employee Object 2

For the Employee Object, we have the following data.

Name = Ankit
ID = 1
Designation = Vice President
Address = Pune

Java Codes

Employee class

It is a Java Bean that represents an Employee Object. Two things worth highlighting in these codes.

The class implements the Diffable interface
The class overrides the diff method
- This is where the magic happens

import org.apache.commons.lang3.builder.DiffBuilder;
import org.apache.commons.lang3.builder.DiffResult;
import org.apache.commons.lang3.builder.Diffable;
import org.apache.commons.lang3.builder.ToStringStyle;

public class Employee  implements Diffable<Employee>{

    private int id;
    private String name;
    private String designation;
    private String address;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDesignation() {
        return designation;
    }

    public void setDesignation(String designation) {
        this.designation = designation;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public DiffResult diff(Employee obj) {
        return new DiffBuilder(this, obj, ToStringStyle.SHORT_PREFIX_STYLE)
                .append("id", this.id, obj.id)
                .append("name", this.name, obj.name)
                .append("designation", this.designation, obj.designation)
                .append("address", this.address, obj.address)
                .build();
    }
}

DiffableDemo class

This is the main class – the entry point.

import org.apache.commons.lang3.builder.Diff;
import org.apache.commons.lang3.builder.DiffResult;

public class DiffableDemo {

    public static void main(String[] args) {
        Employee avpEmp = new Employee();
        avpEmp.setId(1);
        avpEmp.setName("Ankit");
        avpEmp.setAddress("Mumbai");
        avpEmp.setDesignation("Assistance Vice President");

        Employee vpEmp = new Employee();
        vpEmp.setId(1);
        vpEmp.setName("Ankit");
        vpEmp.setAddress("Pune");
        vpEmp.setDesignation("Vice President");


        DiffResult diff = avpEmp.diff(vpEmp);

        for(Diff<?> d: diff.getDiffs()) {
            System.out.println(d.getFieldName()
                    + "= FROM[" + d.getLeft() + "] TO [" + d.getRight() + "]");
        }
        System.out.println();
    }
}

This outputs:

title= FROM[Mumbai] TO [Pune]
content= FROM[Assistance Vice President] TO [Vice President]

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